Piston



May 20, 1930.

F. JARDINE PISTON Filed Sept. 23, 1926 INVENTQR M YM ATTORNEYS steel or iron members for restraining or con- Patented May 20, 1930 UNITED STATES PATENT OFFICE FRANK JARDINE, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE ALUMINUM COMPANY OF AMERICA, 01? PITTSBURGH, PENNSYLVANIA, A CORPORA- TION OF PENNSYLVANIA PISTON Application filed September 23, 1926. Serial No. 137,194.

This invention relates to a piston. It is particularly applicable to pistons composed of different materials, which, having different coeflicients of expansion, tend to produce great internal stresses in the piston when cast.

Many pistons are made of different materials, as for example aluminum or aluminum alloy pistons in which are incorporated trolling the expansion of the more expansible material. This type of piston is claimed broadly in my co-pending application, Serial No. 47,214, filed July 31, 1925. A common way of forming such pistons is to cast the main part of the piston about the control members so that these are at least partly embedded therein. Upon cooling after the casting operation, the different materials tend to contract at different rates and to thus set up great internal stresses in the piston.

It is an object of this invention to provide a piston in which substantially all internal stresses have been relieved.

Other objects will hereinafter appear.

The invention will be better understood from the description of one practical embodiment thereof illustrated in the accom panying drawings, in which Fig. l is a side elevation of a finished piston made according to the invention. I

Fig. 2 is a longitudinal section thereof taken on the line 22 of Fig. 1. v

Fig. 3 is a bottom plan view of the piston, and

Fig. 4 is a view similar to Fig. 1, but showing the piston casting before machining.

The piston has a head consisting of a top 1 and a depending annular flange 2 which may be provided with grooves 3 for the usual piston rings (not shown). Also depending from the head are walls 4 which carry wrist pin bosses 5 and 6 and are strengthened and stiffened by-webs 7 and 8.

Below the piston head is a skirt comprising bearing or thrust faces 9 and 10 which are joined beneath the wrist pin bosses by strapboss carrying walls by control members A and B, shown as hollow squares having their ends embedded in ridges 13 on the inside of the bearlng faces, and their sides spanning the spacebetween the bearing faces, with the lntermediate parts of the sides embedded in the boss carrying walls. The control members are of a material, such as iron, steel, lnvar and the like, which will cause the diameter of the piston-t0 change only as desired, for instance at the rate of change of the cylinder in which it operates.

The connectors 11 are split at 14 and the splits spanned by arcuate bridges or culverts 15, the splits and culverts allowing for the perlmetrical expansion of the skirt.

Bearing face 9 is shown joined to the piston head by a relatively narrow neck or web 16 while bearing face 10 is separated from the head by an air gap 17.

The piston is made as follows The control members A and B are placed in a mold and the balance of the piston cast around them. The different contraction of the varlous parts of the piston upon cooling, of course, 1nduces severe internal stresses therein. The piston, before machining, is as shown 1n Fig. 4. Both bearing faces 9 and 10 are jolned to the head flange 2 by webs 16 and 18, respectively. These webs are located centrally of the bearing faces and the outer parts of'the faces are separated from flange 2 by cored slots 19. These cored slots permit the outer edges of the hearing or thrust faces to which edge portions the control membersare secured to adjust themselves independently of the head and so prevent the production of some stresses both in the faces and head. For example, as the skirt and control members contract upon cooling, the skirt when made of an aluminum alloy contracts to a much greater extent than the control members when the latter are made of honor steel. Consequently when the portions of the skirt sections between the control members shrink inwardly, the portions of the skirt sections attached to the control'members tend to remain stationary and therefore a lateral pressure is applied thereto which tends to bend these portions of the skirt sections outwardly. Also the shrinkage of the skirt sec tions between the control members draws the latter laterally and the control members tend to become bent.

After casting, one or both bearing faces may be separated from the head by cuttin either or both necks. In the drawings, necl 18 is shown as cut away, separating bearing face 10 from the piston head. This operation relieves some of the stresses within the piston so that the control members and portions of the skirt attached thereto can assume their original shape.

After this, the piston is heat treated for a considerable period at a relatively low temperature. A temperature of 300 F. for a period of 50 hours has been found to give satisfactory results. This long heat treatment relieves practically all the remaining stresses.

After this heat treatment the piston may be machined without tending to deform itself, thus considerably facilitating its manufacture.

My copending application, Serial No. 79,527, filed January 6, 1926, contains claims based on piston construction somewhat similar to that shown in this application.

The method of heat treatment disclosed in this application is claimed in my copending application, Serial No. 262,641, filed on or about March 19, 1928, as a division of this present application.

While I have described one embodiment of my invention with some particularity, I do not limit myself to the precise details shown, but claim as my inventionall variations and modifications, thereof coming within the scope of the appended claims.

I claim- 1. A piston having a head, and a skirt comprislng two spaced bearing faces, one of which is inte rally joined to the head at its center by rigid connecting portion lying in the cylindrical surface of the head and skirt and s aced therefrom at its sides.

2. piston comprising a head, a skirt including opposed sections having bearing faces, control members of material of a different coefiicient of expansion than the material of the skirt secured rigidly to and connecting opposed sections, one of the sections being directly afiixed to the head intermediate the portions thereof securedto the control members. Y

3. A piston comprising a head, a skirt including opposed sections having bearing faces, control members of material of a lowercoeflicient of expansion than the material of the skirt connecting opposed sections to conti'ol relative outward movement thereof, one of the sections being affixed to the'head intermediate the portions thereof secured to the control members.

4. A piston comprlsing a head, a skirt including opposed sections having bearing faces, control members of material of a lower coefficient of expansion than the material of the skirt connecting opposed sections at opposite sides thereof to control relative outward movement of the sections, one of the sections being directly aflixed to the head intermediate the portions thereof secured to the control members.

5. A piston comprising a head, a skirt including opposed sections having bearing faces, control members of material of a different coefficient of expansion than the material of the skirt secured rigidl to and connecting opposed sections, one o the sections being directly aflixed to the head intermediate the portions thereof connected to the control members, the opposed section being movable relative to the head;

6. A piston comprising a head, boss carrying walls depending therefrom, a skirt including opposed sections having bearing faces and resiliently joined together below the walls, control members different coefficient of expansion than the material of the skirt secured rigidly to and connecting opposed sections, one of the sections being directly aflixed to the head intermediate the portions thereof connected to the control members.

In testimony whereof I hereunto afiix my signature this 20th day of September, 1926.

- FRANK JARDINE.

of material of a CERTIFICATE or CORRECTION.

Patent No. 1,759,508. I A v Granted May 20, 1930, to

FRANK JARDINE.

It is hereby certified that the above numbered patent was erroneously issued to "The Aluminum Company of America", whereas said patent should have been issued to The Cleveland Trust Company, Trustee, of Cleveland, Ohio, a Corporation of Ohio, said Corporation, being assignee by mesne assignments of the entire interest in said invention, as shown by the record of assignments in this of lice; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of August, A. D. 1930.

M. J.'Moore, (Seal) Acting Commissioner of Patents. 

